Radio frequency identification (RFID) is an automatic identification technology with ability to wireless communication (read and write data without direct contact) and without the necessity for line-of-sight, such that it is convenient, easy to use and well suited for automatic operation and can function under a variety of environment conditions while providing a high level of data integrity. RFID is a technology with bright future and is going to replace the conventional bar coding system for many companies and organizations. The RFID system, mainly consisted of RFID tags, readers and a computer system, can be implemented by various applications and produced by many different manufacturers.
Nevertheless, there is no any current RFID system that has the ability to achieve 100 percent reading rate, especially for those using passive RFID tags. The unsatisfactory reading rate may be caused by several reasons. One of the reasons is the adverse effect caused by the material to which a RFID tag is attached thereto, e.g. an absorbent material, such as water, is capable of absorbing electromagnetic waves emitting from a RFID reader for interrogating the tag; and a reflective material, such as metal, is capable of reflecting the electromagnetic waves. Another cause of poor reading rate is that RFID tags, being attached to objects placed in the center of a pile composed of such objects regrouped within a support (case, box, pallet, etc.), are not able to transmit signals out of the pile. Please refer to FIG. 1, which shows a group of objects being stacked and placed on a pallet. As seen in FIG. 1, each object 11 is tagged by a RFID tag 111 whereas there are a plurality of such objects 11 being stacked as a pile and placed on a pallet 10. It is obvious that the RFID tags attached to those objects hidden deeply inside the pile might not be able to be inquired and read correctly. Thus, such pile of objects might cause erroneous information to be registered into the RFID system. Generally, the former cause can be mended by improving the antenna design of RFID tag, such as the near field design by Impinj. However, the improved antenna has little effect on those objects hidden in the pile.
Therefore, it is in need of a method and system for reading and identifying RFID tag that can overcome the aforesaid problems troubling those prior-art RFID systems.